When a disc is suspended vertically by thin lines in sound field, this device can be rotated around an axis to measure the intensity of sound and a simple Rayleigh disk. In this paper, this phenomenon is theoretically analyzed and modified from field theory point of view. The relationship between sound intensity and rotation angle of disk is analyzed. The accuracy of the device is studied deeply through calibration experiments. The influence of relevant parameters on the accuracy of Rayleigh disk is explained. The optimal parameter for designing the Rayleigh disk device is determined.